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Plug-in hybrid cars emit almost 5x greater global warming emissions than lab-reported data indicate, as per a recent analysis.

Growing Discrepancy Between Official and Real-World Emissions

Data shows that PHEVs emit just one-fifth less CO₂ than conventional gas and diesel vehicles, based on analysis carried out by a non-profit organization. That contrasts significantly with lab tests, which assumed a 75% decrease in emissions.

Researchers examined information from in-vehicle energy use monitors of 800,000 vehicles registered in Europe between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, up from three and a half times in 2021.

“Actual CO2 output are increasing, while official emissions are falling,” stated a senior researcher participating in the report. “This gap is growing and creates a serious issue. Consequently, PHEVs emit almost as much as petrol vehicles.”

Primary Reasons Driving the Discrepancy

Researchers linked the majority of the difference to overestimates of the “utility factor” – the ratio of miles driven in electric mode compared to overall mileage. They found that only a quarter of driving was done in EV mode, while official estimates assumed over four-fifths.

Additionally, when running in EV mode, emission levels were significantly higher than official projections. This happened because electric motors were not strong sufficient to function independently, leading to combustion motors burning fossil fuels for nearly one-third of the travel covered in EV mode.

Policy and Financial Consequences

According to estimates, the lowballing of PHEV CO2 output allowed four large automaker groups to escape over €5bn in fines between 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs would pay about €500 extra annually in operating expenses than is assumed under laboratory conditions.

“The bold statements that automakers often promote about their plug-in hybrid vehicles are clearly far from the mark,” commented a automotive expert. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are little improved than standard petrol and diesel cars in terms of fuel consumption, CO₂ production, and operating costs.”

Policy Discussion and Industry Lobbying

Plug-in hybrid vehicles have lately been drawn back into policy discussions as carmakers have lobbied the EU to relax CO₂ targets. A planned ban on sales of new combustion engine cars in 2035 has faced heavy lobbying from the automotive sector and resistance from EU countries with large car industries.

Some high-level politicians have proposed PHEVs as a potential “compromise” solution to include in the regulation.

An external energy policy specialist, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after a long period in which segments of the automotive industry argued there was too little information to properly assess actual CO2 output.

“These findings demonstrate, without question, that the gap in lab and real-world PHEV energy use and CO₂ output is much, much greater than for petrol or diesel vehicles,” they said. “Any policy changes concerning PHEVs should be made with utmost caution and in the light of this evidence.”